For this reason, as well as the ambiguity of the impact of AQP4 on the neurological outcome of cerebral edema, attempts to translate somehow the positive results of in vivo studies into clinical practice should await more precise and more critical benefit-risk calculations for an inhomogeneous group of conditions, in which brain edema and/or neurovascular uncoupling play a major role. The gene discussed is AQP4; the disease is brain edema.